The present invention relates to a method for reducing interference and saving energy consumption in a cellular network, in particular to a base station with sleeping function in a cellular network and a distributed base station sleep control method.
In recent years, with the rapid increase of demand for wireless data traffic, energy consumption of cellular networks increases rapidly. In view of expenses of operators in terms of economy and carbon dioxide emission in terms of environment protection, many companies and research organizations in the world are currently developing technologies for reducing energy consumption of cellular networks. It is most efficient to decrease energy consumption of base stations since the energy consumption of base stations in a cellular network accounts for the largest proportion of that of the entire network. There is a plurality of implementations for saving base station energy consumption, which includes improving hardware design (for example adopting energy efficient power amplifier and fan-free chiller), resource allocation (for example power control), and base station deployment optimization and so on. However, the expected saved energy consumption by improving hardware design and resource allocation is limited, since base stations in operation still consume quite a lot of energy.
Since the traffic in a cellular network is very non-uniform in terms of temporal and spatial distribution, and base stations are generally deployed and operated based on their peak traffic design, base stations would not be taken full advantage of to a great extent. Therefore, a dynamic base station sleep mechanism causes the system to completely switch off some base stations that are under utilized rather than shutting down radio transceivers during low traffic hours such as nights, which could greatly reduce waste of energy. When some base stations are switched off and hence are in sleep mode, surrounding active base stations need to know and cover blank areas and ensure coverage of sleeping cells by their power amplification. This concept of self-organizing networks has been introduced into standards for 3GPP (3GPP TS32.521) for adding network intelligent functions, enabling a network to optimize and re-configure so as to reduce costs and enhance network performance and flexibility.
Base station sleep mechanism is classified into central control and distributed types. The central control type base station sleep can optimize base station sleep, and reduce the maximum energy consumption while ensuring coverage and user service quality. However it requires the traffic of all cells and channel state between users and surrounding base stations. Therefore, it is highly complex to implement the central control type base station sleep mechanism, and signaling needed to be exchanged between base stations and control nodes will increase. Thus, it is desired to develop a distributed base station sleep mechanism that allows a base station to detect traffic and to determine to enter sleep state by itself.
Patent document 1 (CN 102421172A) “Base Station, User Equipment and Method for Saving Base Station Energy Consumption” discloses a base station sleep method. This method only considers partial sleep state. When a base station detects that no user needs to be served in a period of time, it shuts down its transmitter while the receiver remain active. Patent document 2 (US2012/0106423 A1) “Energy efficient base station entering sleep mode” discloses a method for a base station to enter sleep state and wake up. This method only considers entering sleep state when there is no user to be served in a cell. The non-patent document 1 proposed a centralized high complexity algorithm and a distributed sleep mechanism. With this distributed method, a user is handed over to a neighboring cell when some base stations are in low traffic and then the base stations enter sleep state themselves. This method requires the user to exchange information with base stations, which causes increase of battery consumption of a user terminal.